Sound-absorbing unit



Aug. 29, 1944. w K, 3 ETAL 2,357,115

SOUND-ABSORBING UNIT Filed March 10, 1942 25m 24 S 1 2a Z4 a A/voxe w4/5 2AA TroRNEY Patented Aug. 29, 1944 UNITED STATES PATENT OFFICE SOUND-ABSORBING UNIT William A. Jack, 3rd, North Plainfield, and AndrewMenzak, Jr., Manville, N. J.

Application March 10, 1942, Serial No. 434,034

Claims.

The present invention relates to acoustical constructions, and, moreparticularly, to improved, self-contained. sound-absorbing units.

Heretofore, a type of sound-absorbing units has been employed inacoustical treatments, the units comprising pads of fibrous materialsuch as mineral wool, wood fibre, hair felt, or the like. The pads areemployed either directly as the wall treatment or as elements of atreatment including a foraminous pan or sheet forming a facing andsupporting member for the pad.

The instant invention is concerned with a unit of the general typereferred to above and has for its principal object the provision of suchunit, which may be lighter in weight and thinner than the unitsheretofore employed while retaining at least the sound-absorbingefficiency of the prior constructions.

Another object of the invention is the provision of a self-containedunit of the type referred to, involvin both a porous sound-absorbingmeans, such as a fibrous felt, and a vibratile diaphragm.

A further object of the invention is the provision of such unit adaptedfor use, per se, as a wall facing material, or as a component of asystem including sound-pervious facing and supporting elements such asthe perforated pans illustrated in patent to Norris No. 1,726,500,issued August 27, 1929.

Our invention will be more fully understood and further objects andadvantages thereof will become apparent when reference is made to themore detailed description. thereof which is to follow and to theaccompanying drawing, in which:

Fig. 1 is a sectional view through a ceiling or wall, illustrating unitsof the inventionapplied thereto Fig. 2 is a perspective view with partsbroken away for clearness of illustration, depicting a sound-absorbingunit in accordance with the invention; and

Fig. 3 is a sectional view taken on the line 3-3 of Fig. 2.

Referring now to the drawing, and more particularly to Figs. 2 and 3, aunit in accordance ,with the invention comprises a pad III of asoundabsorbing material. Preferably, the pad is a felted body of mineralwool fibres, hair felt, wood fibre, or the like. However, in someinstances a loose, fibrous, or granular material, or a porous block suchas a ceramic block, may'be employed. Pad l0 acts to absorb sound throughsound decadence in the numerous interstices and openings providedtherein by the fibrous or granular structure, and is particularlyeffective with respect to sounds of the higher frequencies, say,

to be exposed to the sound to be absorbed is a vibratile diaphragm l2,preferably comprising a heavy paper, kraft paper, or the like. It hasbeen determined that a kraft paper weighing 0,021 pound per square footis suitable for this purpose, but it will be understood that theparticular weight is not critical although a relativcly heavy paper ipreferred. To increase the weight of the diaphragm, it suitably carriesa coating and impregnating material, for example, asphalt, as indicatedat it. Here, again, the weight of the asphalt to be employed may varywide y, but, for example, may be,'say, three times or more the weight ofthe paper. Diaphragm i2 is preferably adhesively secured to the rearface of the pad III, the asphalt coating l4 suitably acting as thadhesive for this purpose. Alternatively, the diaphragm may rest looselyon the rear face of the pad. The diaphragm is particularly effective toabsorb sounds of the lower frequencies, say, those below 500 cycles persecond.

Surrounding the pad l0 and the diaphragm i2 is a wrapper 16 of thin,flexible sheet'material which may be substantially impervious to air.

Preferably, the wrapper is folded as indicated in Fig. 2, and theoverlapping portions, including the lapping edge l8 and tabs 20, aresecured to the paper therebelow by a suitable adhesive as indicated at.per l6 may be a lightweight kraft paper, asbestos paper, or a foil orfilm may be used if desired. A kraft paper weighing, say, 0.011 poundper square foot has been found to be satisfactory. Where kraft paper orsimilar inflammable materials are employed, they may be renderednoninflammable by any conventional treatment for this purpose.

The units of the instant invention are employed in any desired manner inan acoustical treatment, for example, as illustrated in Fig. 1. In thisfigure, the units are shown as supported from furring strips 24 carriedby the permanent ceiling or wall 26. The attachment between the unitsand furring strips may be made in any desired manner and, asillustrated, comprises an adhesive 28.

In lieu of the furring strip supporting means shown, the units, may beemployed in pans of the type disclosed, for example, in the NorrisPatent No. 1,726,500, previously referred to, the pans,

The paper constituting wrapin turn, being supported from the permanentwall by suitable T-bars or the like.

The inclusion of the diaphragm H with the sound-absorbing pad ID in asingle wrapper [6 provides a self-contained, individual unit havingsuperior sound-absorbing characteristics to thicker and heavier units asheretofore employed in which a sound-absorbing body or pad alone isused. The unit of the invention is particularly applicable whererelatively lightweight and inexpensive treatments are desired, but wherehigh sound-absorbing efiiciency must be maintained. The wrapper, inaddition to maintaining the diaphragm and pad in proper relationship,serves to prevent the sifting out of loose or granular material from thepad, and also prevents breathlng through the pad.

Having thus described our invention in rather full detail, it will beunderstood that these details need not be strictly adhered to, but thatvarious changes and modifications will suggest themselves to one skilledin the art, all falling within the scope of the invention as defined bythe subjoined claims.

What we claim is: r

1. A sound absorbing unit comprising a porous, fibrous, self-sustainingbody of sound absorbing material, a relatively flexible, fibrous sheetof a character to be vibrated to have a substantial sound-absorbingfunction when subjected to sound having a frequency of the order of 500cycles per second and lower, overlying a rear face of said body, animperforate wrapper inclosing said body and sheet, said wrapperincluding a light weight relatively flexible panel, overlying the frontface of said body and adapted to transmit sounds of both high and lowfrequency.

2. A sound absorbing unit comprising a porous, fibrous body of soundabsorbing material, a relatively flexible, fibrous sheet including aweighting material, said weighted sheet being of a character to bevibrated to have a substantial soundabsorbing function when subjected tosound having frequencies of the order of 500 cycles per second andlower, overlying a rear face of said body, an impcrforate wrapperinclosing said body and sheet, said wrapper comprising a light weightrelatively flexible section overlying the front face of said body andadapted to transmit sounds of both high and low frequency.

3. A sound absorbing unit comprising a porous, fibrous, self-sustainingbody of sound absorbing material, a relatively flexible, fibrous,asphalt coated sheet of a character to be vibrated to have a substantialsound-absorbing function when subjected to sound having frequencies ofthe order of 500 cycles per second and lower, overlying the rear face ofsaid body, a light weight relatively flexible, imperforate wrapperinclosing said body and sheet, the portion of said wrapper overlying thefront face of said body, being adapted to transmit sounds of both highand low frequency.

4. A sound absorbing construction comprising a plurality of units, eachof which include a porous self-sustaining, fibrous body of soundabsorbing material, a relatively flexible, fibrous sheet of a characterto be vibrated to have a substantial sound-absorbing function whensubjected to sound having frequencies Of the order of 500 cycles persecond and lower overlying a rear face of said body, and an imperforatewrapper inclosing said body and sheet, said wrapper including a lightweight relatively flexible panel, overlying the front face of the bodyand adapted to transmit sounds of both high and low frequencies, saidunits lying in substantially edgewise contiguous relationship andforming the interior surface of the construction, and means supportingsaid units in fixed spaced relationship to a wall surface.

5. A sound absorbing construction comprising a plurality of units, eachof said units including a porous self-sustaining, fibrous body of soundabsorbing material, a relatively flexible, weighted, fibrous sheet of acharacter to be vibrated to have a substantial sound-absorbing functionwhen subjected to sound having frequencies of the order of 500 cyclesper second and lower overlying a rear face of said body, an imperioratewrapper comprising a light weight relatively flexible paper inclosingsaid body and sheet, said wrapper having a panel overlying the frontface of said body adapted to transmit sounds of both high and lowfrequencies, said units lying in edgewise adjacent relationship andforming the interior surface of said construction, and means supportingsaid units in fixed spaced relationship to a wall.

WILLIAM A. JACK, 3m). ANDREW MENZAK, JR.

